Edward Lefebre, Brooklyn, to David Blakely, New York, 6 February 1894, Blakely Papers, Special Collections, New York Public Library, New York.
There is a number of diferent stories about the examples set for the american saxophone. One such story tells us about a quartet of Ad. Sax instruments saved from the battlefield of El Caney in 1898 which were then judged by Lefebvre te be inferior to the modern, improved Conn instruments. If this story has something of truth in it, it implies that F. A. Buescher's designs were not based on Ad. Sax's. A fine source to read is the study by James Noyes, which also discusses the starting year of american production. Dates vary from 1885 up to 1890.
Lefebvre may have been a consultant for Conn before Buescher's departure. However, the C. G. Conn's Truth 3, no. 5 (January 1896) suggests, again according to Noyes, that Lefebvre was not employed in the Conn factory until 1895, while Buescher left the Conn company in 1893. If that's true, the examples set to american saxophone making are even more undefined still.